Allow return key in tab order

I am currently replacing an old application where users can enter different text, press buttons, ... in order to do their work.
Those users are used to have a specific tab order for different tasks.
E.g.: Tab|Return|Tab|Tab|Return

Unfortunately the tab order system in Qt using tab stops doesn't accept events by the return key and only allows the space bar as a signal emitter.
So user's would have to do the following in my rewritten app: Tab|Space|Tab|Tab|Space
(I'm using Qt 5.7, I don't know which framework the old app used, might even be native Win32).

I got some requests by users to change that behaviour back so they can use their good old 'return'-keys instead of the evil and mean space-bar. Yippiyeah!

Is there any way to do this? I thought about filtering the TabKey-Event and set the auto-default value for each widget. But as far as I am aware those tab-events are filtered by the top-widget itself in order to process the focus changes? At least I didn't manage to capture any.

Are there any other possible solutions I am missing or might I have to reimplement the QWidget class in the end?